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package javax.tools;

import java.io.File;
import java.io.Writer;
import java.nio.charset.Charset;
import java.util.Locale;
import java.util.concurrent.Callable;
import javax.annotation.processing.Processor;

/**
 * Interface to invoke Java&trade; programming language compilers from programs.
 *
 * <p>The compiler might generate diagnostics during compilation (for example, error messages).  If
 * a diagnostic listener is provided, the diagnostics will be supplied to the listener.  If no
 * listener is provided, the diagnostics will be formatted in an unspecified format and written to
 * the default output, which is {@code System.err} unless otherwise specified.  Even if a diagnostic
 * listener is supplied, some diagnostics might not fit in a {@code Diagnostic} and will be written
 * to the default output.
 *
 * <p>A compiler tool has an associated standard file manager, which is the file manager that is
 * native to the tool (or built-in).  The standard file manager can be obtained by calling
 * {@linkplain #getStandardFileManager getStandardFileManager}.
 *
 * <p>A compiler tool must function with any file manager as long as any additional requirements as
 * detailed in the methods below are met.  If no file manager is provided, the compiler tool will
 * use a standard file manager such as the one returned by {@linkplain #getStandardFileManager
 * getStandardFileManager}.
 *
 * <p>An instance implementing this interface must conform to <cite>The Java&trade; Language
 * Specification</cite> and generate class files conforming to <cite>The Java&trade; Virtual Machine
 * Specification</cite>. The versions of these specifications are defined in the {@linkplain Tool}
 * interface.
 *
 * Additionally, an instance of this interface supporting {@link javax.lang.model.SourceVersion#RELEASE_6
 * SourceVersion.RELEASE_6} or higher must also support {@linkplain javax.annotation.processing
 * annotation processing}.
 *
 * <p>The compiler relies on two services: {@linkplain DiagnosticListener diagnostic listener} and
 * {@linkplain JavaFileManager file manager}.  Although most classes and interfaces in this package
 * defines an API for compilers (and tools in general) the interfaces {@linkplain
 * DiagnosticListener}, {@linkplain JavaFileManager}, {@linkplain FileObject}, and {@linkplain
 * JavaFileObject} are not intended to be used in applications.  Instead these interfaces are
 * intended to be implemented and used to provide customized services for a compiler and thus
 * defines an SPI for compilers.
 *
 * <p>There are a number of classes and interfaces in this package which are designed to ease the
 * implementation of the SPI to customize the behavior of a compiler:
 *
 * <dl> <dt>{@link StandardJavaFileManager}</dt> <dd>
 *
 * Every compiler which implements this interface provides a standard file manager for operating on
 * regular {@linkplain java.io.File files}.  The StandardJavaFileManager interface defines
 * additional methods for creating file objects from regular files.
 *
 * <p>The standard file manager serves two purposes:
 *
 * <ul> <li>basic building block for customizing how a compiler reads and writes files</li>
 * <li>sharing between multiple compilation tasks</li> </ul>
 *
 * <p>Reusing a file manager can potentially reduce overhead of scanning the file system and reading
 * jar files.  Although there might be no reduction in overhead, a standard file manager must work
 * with multiple sequential compilations making the following example a recommended coding pattern:
 *
 * <pre>
 *       File[] files1 = ... ; // input for first compilation task
 *       File[] files2 = ... ; // input for second compilation task
 *
 *       JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
 *       StandardJavaFileManager fileManager = compiler.getStandardFileManager(null, null, null);
 *
 *       {@code Iterable<? extends JavaFileObject>} compilationUnits1 =
 *           fileManager.getJavaFileObjectsFromFiles({@linkplain java.util.Arrays#asList
 * Arrays.asList}(files1));
 *       compiler.getTask(null, fileManager, null, null, null, compilationUnits1).call();
 *
 *       {@code Iterable<? extends JavaFileObject>} compilationUnits2 =
 *           fileManager.getJavaFileObjects(files2); // use alternative method
 *       // reuse the same file manager to allow caching of jar files
 *       compiler.getTask(null, fileManager, null, null, null, compilationUnits2).call();
 *
 *       fileManager.close();</pre>
 *
 * </dd>
 *
 * <dt>{@link DiagnosticCollector}</dt> <dd> Used to collect diagnostics in a list, for example:
 * <pre>
 *       {@code Iterable<? extends JavaFileObject>} compilationUnits = ...;
 *       JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
 *       {@code DiagnosticCollector<JavaFileObject> diagnostics = new
 * DiagnosticCollector<JavaFileObject>();}
 *       StandardJavaFileManager fileManager = compiler.getStandardFileManager(diagnostics, null,
 * null);
 *       compiler.getTask(null, fileManager, diagnostics, null, null, compilationUnits).call();
 *
 *       for ({@code Diagnostic<? extends JavaFileObject>} diagnostic :
 * diagnostics.getDiagnostics())
 *           System.out.format("Error on line %d in %s%n",
 *                             diagnostic.getLineNumber(),
 *                             diagnostic.getSource().toUri());
 *
 *       fileManager.close();</pre>
 * </dd>
 *
 * <dt> {@link ForwardingJavaFileManager}, {@link ForwardingFileObject}, and {@link
 * ForwardingJavaFileObject} </dt> <dd>
 *
 * Subclassing is not available for overriding the behavior of a standard file manager as it is
 * created by calling a method on a compiler, not by invoking a constructor.  Instead forwarding (or
 * delegation) should be used.  These classes makes it easy to forward most calls to a given file
 * manager or file object while allowing customizing behavior.  For example, consider how to log all
 * calls to {@linkplain JavaFileManager#flush}:
 *
 * <pre>
 *       final {@linkplain java.util.logging.Logger Logger} logger = ...;
 *       {@code Iterable<? extends JavaFileObject>} compilationUnits = ...;
 *       JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
 *       StandardJavaFileManager stdFileManager = compiler.getStandardFileManager(null, null,
 * null);
 *       JavaFileManager fileManager = new ForwardingJavaFileManager(stdFileManager) {
 *           public void flush() throws IOException {
 *               logger.entering(StandardJavaFileManager.class.getName(), "flush");
 *               super.flush();
 *               logger.exiting(StandardJavaFileManager.class.getName(), "flush");
 *           }
 *       };
 *       compiler.getTask(null, fileManager, null, null, null, compilationUnits).call();</pre>
 * </dd>
 *
 * <dt>{@link SimpleJavaFileObject}</dt> <dd>
 *
 * This class provides a basic file object implementation which can be used as building block for
 * creating file objects.  For example, here is how to define a file object which represent source
 * code stored in a string:
 *
 * <pre>
 *       /**
 *        * A file object used to represent source coming from a string.
 *        {@code *}/
 *       public class JavaSourceFromString extends SimpleJavaFileObject {
 *           /**
 *            * The source code of this "file".
 *            {@code *}/
 *           final String code;
 *
 *           /**
 *            * Constructs a new JavaSourceFromString.
 *            * {@code @}param name the name of the compilation unit represented by this file
 * object
 *            * {@code @}param code the source code for the compilation unit represented by this
 * file object
 *            {@code *}/
 *           JavaSourceFromString(String name, String code) {
 *               super({@linkplain java.net.URI#create URI.create}("string:///" +
 * name.replace('.','/') + Kind.SOURCE.extension),
 *                     Kind.SOURCE);
 *               this.code = code;
 *           }
 *
 *           {@code @}Override
 *           public CharSequence getCharContent(boolean ignoreEncodingErrors) {
 *               return code;
 *           }
 *       }</pre>
 * </dd> </dl>
 *
 * @author Peter von der Ah&eacute;
 * @author Jonathan Gibbons
 * @see DiagnosticListener
 * @see Diagnostic
 * @see JavaFileManager
 * @since 1.6
 */
public interface JavaCompiler extends Tool, OptionChecker {

  /**
   * Creates a future for a compilation task with the given
   * components and arguments.  The compilation might not have
   * completed as described in the CompilationTask interface.
   *
   * <p>If a file manager is provided, it must be able to handle all
   * locations defined in {@link StandardLocation}.
   *
   * <p>Note that annotation processing can process both the
   * compilation units of source code to be compiled, passed with
   * the {@code compilationUnits} parameter, as well as class
   * files, whose names are passed with the {@code classes}
   * parameter.
   *
   * @param out a Writer for additional output from the compiler; use {@code System.err} if {@code
   * null}
   * @param fileManager a file manager; if {@code null} use the compiler's standard filemanager
   * @param diagnosticListener a diagnostic listener; if {@code null} use the compiler's default
   * method for reporting diagnostics
   * @param options compiler options, {@code null} means no options
   * @param classes names of classes to be processed by annotation processing, {@code null} means no
   * class names
   * @param compilationUnits the compilation units to compile, {@code null} means no compilation
   * units
   * @return an object representing the compilation
   * @throws RuntimeException if an unrecoverable error occurred in a user supplied component.  The
   * {@linkplain Throwable#getCause() cause} will be the error in user code.
   * @throws IllegalArgumentException if any of the options are invalid, or if any of the given
   * compilation units are of other kind than {@linkplain JavaFileObject.Kind#SOURCE source}
   */
  CompilationTask getTask(Writer out,
      JavaFileManager fileManager,
      DiagnosticListener<? super JavaFileObject> diagnosticListener,
      Iterable<String> options,
      Iterable<String> classes,
      Iterable<? extends JavaFileObject> compilationUnits);

  /**
   * Gets a new instance of the standard file manager implementation
   * for this tool.  The file manager will use the given diagnostic
   * listener for producing any non-fatal diagnostics.  Fatal errors
   * will be signaled with the appropriate exceptions.
   *
   * <p>The standard file manager will be automatically reopened if
   * it is accessed after calls to {@code flush} or {@code close}.
   * The standard file manager must be usable with other tools.
   *
   * @param diagnosticListener a diagnostic listener for non-fatal diagnostics; if {@code null} use
   * the compiler's default method for reporting diagnostics
   * @param locale the locale to apply when formatting diagnostics; {@code null} means the
   * {@linkplain Locale#getDefault() default locale}.
   * @param charset the character set used for decoding bytes; if {@code null} use the platform
   * default
   * @return the standard file manager
   */
  StandardJavaFileManager getStandardFileManager(
      DiagnosticListener<? super JavaFileObject> diagnosticListener,
      Locale locale,
      Charset charset);

  /**
   * Interface representing a future for a compilation task.  The
   * compilation task has not yet started.  To start the task, call
   * the {@linkplain #call call} method.
   *
   * <p>Before calling the call method, additional aspects of the
   * task can be configured, for example, by calling the
   * {@linkplain #setProcessors setProcessors} method.
   */
  interface CompilationTask extends Callable<Boolean> {

    /**
     * Sets processors (for annotation processing).  This will
     * bypass the normal discovery mechanism.
     *
     * @param processors processors (for annotation processing)
     * @throws IllegalStateException if the task has started
     */
    void setProcessors(Iterable<? extends Processor> processors);

    /**
     * Set the locale to be applied when formatting diagnostics and
     * other localized data.
     *
     * @param locale the locale to apply; {@code null} means apply no locale
     * @throws IllegalStateException if the task has started
     */
    void setLocale(Locale locale);

    /**
     * Performs this compilation task.  The compilation may only
     * be performed once.  Subsequent calls to this method throw
     * IllegalStateException.
     *
     * @return true if and only all the files compiled without errors; false otherwise
     * @throws RuntimeException if an unrecoverable error occurred in a user-supplied component.
     * The {@linkplain Throwable#getCause() cause} will be the error in user code.
     * @throws IllegalStateException if called more than once
     */
    Boolean call();
  }
}
